r"""
Server interfaces.

Starting in CherryPy 3.1, cherrypy.server is implemented as an
:ref:`Engine Plugin<plugins>`. It's an instance of
:class:`cherrypy._cpserver.Server`, which is a subclass of
:class:`cherrypy.process.servers.ServerAdapter`. The ``ServerAdapter`` class
is designed to control other servers, as well.

Multiple servers/ports
======================

If you need to start more than one HTTP server (to serve on multiple ports, or
protocols, etc.), you can manually register each one and then start them all
with engine.start::

    s1 = ServerAdapter(
        cherrypy.engine,
        MyWSGIServer(host='0.0.0.0', port=80)
    )
    s2 = ServerAdapter(
        cherrypy.engine,
        another.HTTPServer(host='127.0.0.1', SSL=True)
    )
    s1.subscribe()
    s2.subscribe()
    cherrypy.engine.start()

.. index:: SCGI

FastCGI/SCGI
============

There are also Flup\ **F**\ CGIServer and Flup\ **S**\ CGIServer classes in
:mod:`cherrypy.process.servers`. To start an fcgi server, for example,
wrap an instance of it in a ServerAdapter::

    addr = ('0.0.0.0', 4000)
    f = servers.FlupFCGIServer(application=cherrypy.tree, bindAddress=addr)
    s = servers.ServerAdapter(cherrypy.engine, httpserver=f, bind_addr=addr)
    s.subscribe()

The :doc:`cherryd</deployguide/cherryd>` startup script will do the above for
you via its `-f` flag.
Note that you need to download and install `flup <http://trac.saddi.com/flup>`_
yourself, whether you use ``cherryd`` or not.

.. _fastcgi:
.. index:: FastCGI

FastCGI
-------

A very simple setup lets your cherry run with FastCGI.
You just need the flup library,
plus a running Apache server (with ``mod_fastcgi``) or lighttpd server.

CherryPy code
^^^^^^^^^^^^^

hello.py::

    #!/usr/bin/python
    import cherrypy

    class HelloWorld:
        '''Sample request handler class.'''
        @cherrypy.expose
        def index(self):
            return "Hello world!"

    cherrypy.tree.mount(HelloWorld())
    # CherryPy autoreload must be disabled for the flup server to work
    cherrypy.config.update({'engine.autoreload.on':False})

Then run :doc:`/deployguide/cherryd` with the '-f' arg::

    cherryd -c <myconfig> -d -f -i hello.py

Apache
^^^^^^

At the top level in httpd.conf::

    FastCgiIpcDir /tmp
    FastCgiServer /path/to/cherry.fcgi -idle-timeout 120 -processes 4

And inside the relevant VirtualHost section::

    # FastCGI config
    AddHandler fastcgi-script .fcgi
    ScriptAliasMatch (.*$) /path/to/cherry.fcgi$1

Lighttpd
^^^^^^^^

For `Lighttpd <http://www.lighttpd.net/>`_ you can follow these
instructions. Within ``lighttpd.conf`` make sure ``mod_fastcgi`` is
active within ``server.modules``. Then, within your ``$HTTP["host"]``
directive, configure your fastcgi script like the following::

    $HTTP["url"] =~ "" {
      fastcgi.server = (
        "/" => (
          "script.fcgi" => (
            "bin-path" => "/path/to/your/script.fcgi",
            "socket"          => "/tmp/script.sock",
            "check-local"     => "disable",
            "disable-time"    => 1,
            "min-procs"       => 1,
            "max-procs"       => 1, # adjust as needed
          ),
        ),
      )
    } # end of $HTTP["url"] =~ "^/"

Please see `Lighttpd FastCGI Docs
<http://redmine.lighttpd.net/wiki/lighttpd/Docs:ModFastCGI>`_ for
an explanation of the possible configuration options.
"""

import os
import sys
import time
import warnings
import contextlib

import portend


class Timeouts:
    """Timeout constants."""

    occupied = 5
    free = 1


class ServerAdapter(object):
    """Adapter for an HTTP server.

    If you need to start more than one HTTP server (to serve on multiple
    ports, or protocols, etc.), you can manually register each one and then
    start them all with bus.start::

        s1 = ServerAdapter(bus, MyWSGIServer(host='0.0.0.0', port=80))
        s2 = ServerAdapter(bus, another.HTTPServer(host='127.0.0.1', SSL=True))
        s1.subscribe()
        s2.subscribe()
        bus.start()
    """

    def __init__(self, bus, httpserver=None, bind_addr=None):
        """Initialize the HTTP server plugin."""
        self.bus = bus
        self.httpserver = httpserver
        self.bind_addr = bind_addr
        self.interrupt = None
        self.running = False

    def subscribe(self):
        """Subscribe control methods to the bus lifecycle events."""
        self.bus.subscribe('start', self.start)
        self.bus.subscribe('stop', self.stop)

    def unsubscribe(self):
        """Unsubcribe control methods to the bus lifecycle events."""
        self.bus.unsubscribe('start', self.start)
        self.bus.unsubscribe('stop', self.stop)

    def start(self):
        """Start the HTTP server."""
        if self.running:
            self.bus.log('Already serving on %s' % self.description)
            return

        self.interrupt = None
        if not self.httpserver:
            raise ValueError('No HTTP server has been created.')

        if not os.environ.get('LISTEN_PID', None):
            # Start the httpserver in a new thread.
            if isinstance(self.bind_addr, tuple):
                portend.free(*self.bind_addr, timeout=Timeouts.free)

        import threading

        t = threading.Thread(target=self._start_http_thread)
        t.name = 'HTTPServer ' + t.name
        t.start()

        self.wait()
        self.running = True
        self.bus.log('Serving on %s' % self.description)

    start.priority = 75

    @property
    def description(self):
        """A description about where this server is bound."""
        if self.bind_addr is None:
            on_what = 'unknown interface (dynamic?)'
        elif isinstance(self.bind_addr, tuple):
            on_what = self._get_base()
        else:
            on_what = 'socket file: %s' % self.bind_addr
        return on_what

    def _get_base(self):
        if not self.httpserver:
            return ''
        host, port = self.bound_addr
        if getattr(self.httpserver, 'ssl_adapter', None):
            scheme = 'https'
            if port != 443:
                host += ':%s' % port
        else:
            scheme = 'http'
            if port != 80:
                host += ':%s' % port

        return '%s://%s' % (scheme, host)

    def _start_http_thread(self):
        """Start the HTTP server thread.

        HTTP servers MUST be running in new threads, so that the
        main thread persists to receive KeyboardInterrupt's. If an
        exception is raised in the httpserver's thread then it's
        trapped here, and the bus (and therefore our httpserver)
        are shut down.
        """
        try:
            self.httpserver.start()
        except KeyboardInterrupt:
            self.bus.log('<Ctrl-C> hit: shutting down HTTP server')
            self.interrupt = sys.exc_info()[1]
            self.bus.exit()
        except SystemExit:
            self.bus.log('SystemExit raised: shutting down HTTP server')
            self.interrupt = sys.exc_info()[1]
            self.bus.exit()
            raise
        except Exception:
            self.interrupt = sys.exc_info()[1]
            self.bus.log(
                'Error in HTTP server: shutting down',
                traceback=True,
                level=40,
            )
            self.bus.exit()
            raise

    def wait(self):
        """Wait until the HTTP server is ready to receive requests."""
        while not getattr(self.httpserver, 'ready', False):
            if self.interrupt:
                raise self.interrupt
            time.sleep(0.1)

        # bypass check when LISTEN_PID is set
        if os.environ.get('LISTEN_PID', None):
            return

        # bypass check when running via socket-activation
        # (for socket-activation the port will be managed by systemd)
        if not isinstance(self.bind_addr, tuple):
            return

        # wait for port to be occupied
        with _safe_wait(*self.bound_addr):
            portend.occupied(*self.bound_addr, timeout=Timeouts.occupied)

    @property
    def bound_addr(self):
        """The bind address.

        If it's an ephemeral port and the socket has been bound,
        return the actual port bound.
        """
        host, port = self.bind_addr
        if port == 0 and self.httpserver.socket:
            # Bound to ephemeral port. Get the actual port allocated.
            port = self.httpserver.socket.getsockname()[1]
        return host, port

    def stop(self):
        """Stop the HTTP server."""
        if self.running:
            # stop() MUST block until the server is *truly* stopped.
            self.httpserver.stop()
            # Wait for the socket to be truly freed.
            if isinstance(self.bind_addr, tuple):
                portend.free(*self.bound_addr, timeout=Timeouts.free)
            self.running = False
            self.bus.log('HTTP Server %s shut down' % self.httpserver)
        else:
            self.bus.log('HTTP Server %s already shut down' % self.httpserver)

    stop.priority = 25

    def restart(self):
        """Restart the HTTP server."""
        self.stop()
        self.start()


class FlupCGIServer(object):
    """Adapter for a flup.server.cgi.WSGIServer."""

    def __init__(self, *args, **kwargs):
        """Initialize the flup CGI Server plugin."""
        self.args = args
        self.kwargs = kwargs
        self.ready = False

    def start(self):
        """Start the CGI server."""
        # We have to instantiate the server class here because its __init__
        # starts a threadpool. If we do it too early, daemonize won't work.
        from flup.server.cgi import WSGIServer

        self.cgiserver = WSGIServer(*self.args, **self.kwargs)
        self.ready = True
        self.cgiserver.run()

    def stop(self):
        """Stop the HTTP server."""
        self.ready = False


class FlupFCGIServer(object):
    """Adapter for a flup.server.fcgi.WSGIServer."""

    def __init__(self, *args, **kwargs):
        """Initialize the FCGI server parameters."""
        if kwargs.get('bindAddress', None) is None:
            import socket

            if not hasattr(socket, 'fromfd'):
                raise ValueError(
                    'Dynamic FCGI server not available on this platform. '
                    'You must use a static or external one by providing a '
                    'legal bindAddress.',
                )
        self.args = args
        self.kwargs = kwargs
        self.ready = False

    def start(self):
        """Start the FCGI server."""
        # We have to instantiate the server class here because its __init__
        # starts a threadpool. If we do it too early, daemonize won't work.
        from flup.server.fcgi import WSGIServer

        self.fcgiserver = WSGIServer(*self.args, **self.kwargs)
        # TODO: report this bug upstream to flup.
        # If we don't set _oldSIGs on Windows, we get:
        #   File "C:\Python24\Lib\site-packages\flup\server\threadedserver.py",
        #   line 108, in run
        #     self._restoreSignalHandlers()
        #   File "C:\Python24\Lib\site-packages\flup\server\threadedserver.py",
        #   line 156, in _restoreSignalHandlers
        #     for signum,handler in self._oldSIGs:
        #   AttributeError: 'WSGIServer' object has no attribute '_oldSIGs'
        self.fcgiserver._installSignalHandlers = lambda: None
        self.fcgiserver._oldSIGs = []
        self.ready = True
        self.fcgiserver.run()

    def stop(self):
        """Stop the HTTP server."""
        # Forcibly stop the fcgi server main event loop.
        self.fcgiserver._keepGoing = False
        # Force all worker threads to die off.
        self.fcgiserver._threadPool.maxSpare = (
            self.fcgiserver._threadPool._idleCount
        )
        self.ready = False


class FlupSCGIServer(object):
    """Adapter for a flup.server.scgi.WSGIServer."""

    def __init__(self, *args, **kwargs):
        """Initialize the SCGI server parameters."""
        self.args = args
        self.kwargs = kwargs
        self.ready = False

    def start(self):
        """Start the SCGI server."""
        # We have to instantiate the server class here because its __init__
        # starts a threadpool. If we do it too early, daemonize won't work.
        from flup.server.scgi import WSGIServer

        self.scgiserver = WSGIServer(*self.args, **self.kwargs)
        # TODO: report this bug upstream to flup.
        # If we don't set _oldSIGs on Windows, we get:
        #   File "C:\Python24\Lib\site-packages\flup\server\threadedserver.py",
        #   line 108, in run
        #     self._restoreSignalHandlers()
        #   File "C:\Python24\Lib\site-packages\flup\server\threadedserver.py",
        #   line 156, in _restoreSignalHandlers
        #     for signum,handler in self._oldSIGs:
        #   AttributeError: 'WSGIServer' object has no attribute '_oldSIGs'
        self.scgiserver._installSignalHandlers = lambda: None
        self.scgiserver._oldSIGs = []
        self.ready = True
        self.scgiserver.run()

    def stop(self):
        """Stop the HTTP server."""
        self.ready = False
        # Forcibly stop the scgi server main event loop.
        self.scgiserver._keepGoing = False
        # Force all worker threads to die off.
        self.scgiserver._threadPool.maxSpare = 0


@contextlib.contextmanager
def _safe_wait(host, port):
    """Warn when bind interface is ambiguous.

    On systems where a loopback interface is not available and the
    server is bound to all interfaces, it's difficult to determine
    whether the server is in fact occupying the port. In this case,
    just issue a warning and move on. See issue #1100.
    """
    try:
        yield
    except portend.Timeout:
        if host == portend.client_host(host):
            raise
        msg = 'Unable to verify that the server is bound on %r' % port
        warnings.warn(msg)
